Overexposure to ultraviolet (UV) radiation can be associated with a variety of health conditions. Risks for some of the health conditions can correspond to a person's natural sensitivity to UV exposure and the lifetime UV exposure from both sunlight and artificial sources (e.g., tanning beds and tanning lamps). In addition, physical characteristics (e.g., hair color, eye color, and/or skin color) can be correlated with the risk of skin-related health conditions. Protective measures (e.g., staying indoors or in the shade during peak times during the day, and use of protective clothing) can be taken to reduce the risks of UV overexposure to the skin. Protective measures can also include the application of sunscreen to potentially exposed areas of skin. Although sunscreen can be characterized based on sun protection factor (SPF), the efficacy of the sunscreen as applied to the user's skin may differ based on, for example, the breakdown of one or more active ingredients in the sunscreen can break down, the user's skin sensitivity, the sunscreen's water-resistance.